Set-back device for fuze



Jan. 1 1964 F. c. HUTCHISON ETAL 3,117,522

SET-BACK DEVICE FOR FUZE Filed Nov. 30. 1960 INVENTORS, Frank E-Hur.chisEITL nElLhanm.Fa1es 1%" 0a +4.4 WM

United States atent 3,117,522 SET-BACK DEVICE FOR FUZE Frank C.Hutchison, Greenfield, N.H., and Nathan M. Fales, Westwoo'd, Mass.,assignors, by mesne assignments, to the United States of America asrepresented by the Secretary of the Army Filed Nov. 30, 1960, Ser. No.72,802 1 Claim. (Cl. 102-78) This invention relates to a setback devicefor a fuze and more particularly to a fuze incorporating safety featuresnecessary in the safe handling of artillery type fuzes.

It is a precautionary requirement in the handling of artilleryammunition fuzes that after its assembly to a projectile, the assemblymay be dropped, rolled and otherwise roughly handled without theinitiation of the firing train. It is also essential, that when theprojectile is fired, the explosive train will not function until theprojectile has traveled a sufliciently safe distance from the gun in itstrajectory so as not to injure the gun crew.

It is therefore a primary object of the present invention to provide asetback device for an artillery ammunition fuze to prevent the fuze fromfunctioning until it has traveled a sufficient distance from a gun, whenfired therefrom, in order to provide safety for the gun crew.

It is another object to provide a set-back device for a fuze in which adetonator rotor is first rotated clockwise, then counterclockwise, toalign the detonator with an explosive train, thus affording a time delayin the functioning of the fuze.

A further object is to provide a setback device for a fuze in which thedetonator carrying rotor of the invention is rotated clockwise by anunbalanced mass and then counterclockwise by spring means.

It is a still further object to cause the aforesaid rotor to be lockedin its armed position when finally rotated therein.

The specific nature of the invention as well as other object andadvantages thereof, will clearly appear from a description of apreferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a top plan view of one embodiment of a fuze of the invention,illustrating its approximate position in a projectile, the projectilebeing shown in broken lines;

FIG. 2 is a view of the fuze of FIG. 1, the cover being removed toexpose a portion of the setback mechanism;

FIG. 3 is a cross sectional view taken along line 33 of FIG. 1;

FIG. 4 is an axial sectional view taken along line 44 of FIG. 1;

FIG. 5 is a detail section taken along line 5-5 of FIG. 1; 1

FIG. 6 is a detail section taken along line 66 of FIG. 4; and

FIGS. 7, 8 and 9 are schematic views showing the positions of the rotorduring its travel from a safe to an armed position in the fuze.

Referring to the drawings:

A fuze is indicated generally by 1 and is positioned in a projectile P,the projectile being shown in broken lines. Fuze 1 comprises acylindrical body 2 and is axially bored as at 3 at its rear and as at 4at its frontal portion for providing passageways for an explosive trainfrom a booster (not shown) to a firing pin or like detonating element(also not shown). Body 2 is bored at right angles to bores 3 and 4 as at5 and is counter-bored as at 6 for a purpose which will be apparentlater. A cut out portion '7 is provided for receiving operating elementstherein.

A cylindrical rotor, generally indicated by 8 is mounted for rotation inbore 5 and has a first downwardly depending integral shaft 9 rotatablein counter bore 6.

An unbalanced, sequential mass 10 is located at the under side of rotor8 and is integral therewith for simultaneous rotation together. 1

Rotor 8 carries a detonator 11 in such a location as to lie in the sameaxis as bores 3 and 4 when the rotor is in its armed position in body 2.

A cap 12 is fitted in the cut out portion 7 in body 2 and has a centralopening 13 to receive a shaft 14 integral with the upper portion ofrotor 8 and in axial alignment with shaft 9. A disc 15, having a notch16 in its circumferential edge, is integral with the upper side of rotor8 and shaft 14, and is also received within cap 12 as best seen in FIG.4.

A setback responsive, angular release arm 17 is pivoted to cap 12 by ascrew 18 :and is secured thereon by a cap screw 19. Arm 17 is disposedin spaced relation between the underside of cap 12 and disc 15 and isprovided with a tang 20 at its free end which is adapted to be receivedin notch 16 as is best viewed in FIG. 2.

Rotor 8 is normally urged in a counter clockwise direction by a coilspring 21 which encircles a cap 22 fixed for rotation with shaft 14.Spring 21 has one end received in a slot 23 in shaft 14 and its otherend is held by a screw 24 in cap 12.

Means are provided for locking rotor 8 in its armed and unarmedpositions and consists of a spring biased plunger 25 (see FIG. 3)slidable in a bore 26 and in the safe position of the fuze, plunger 25is in contact with shoulder 28 of the unbalanced arcnate mass 10 whichholds the mass and rotor against rotation.

In operation, assuming that projectile P with fuze 1 attached theretohas left the muzzle of a gun (not shown), projectile spin moves plunger25 out of contact with shoulder 28 of the unbalanced mass 10 and intobore 26 to clear bore 5 thereby freeing unbalanced mass 10 and the rotor8 from its restraining action. At the same time arm 17 is rotatedrearwardly (as shown in FIG. 8) to move tang 20 out of notch 16 in disc15 which also acts to release rotor 8 which then rotates clockwise dueto the influence of set back force upon the unbalanced mass.

Upon cessation of set-back force, rotor 8 is then rotated in acounterclockwise fashion due to the torsion of spring 21 (see FIG. 9)until detonator 11 is aligned with axial bores 3 and 4 to complete theexplosive train and arm the fuze. Plunger 25 now will enter hole 27 inunbalanced mass 10 to prevent detonator 11 from accidently rotating outof alignment with the aforesaid bores and cause malfunction of the fuze.

Other variations and modifications may be effected without departingfrom the scope of the novel concept of the present invention as setforth in the claim.

What is claimed is:

A fuze for attachment to a projectile comprising in combination, a bodyhaving a first axial bore, a second bore normal to and intersecting saidfirst bore, a third bore spaced from and parallel to said second bore,there being a cut-out portion in the outer wall thereof, said cutoutportion being coaxial with said second bore, a dernountable cap receivedin said cut-out portion, a rotor mounted for rotation in said body androtatable about an axis normal to said first bore, upwardly anddownwardly extending shafts integral with said rotor, said shafts beingaxially aligned and journaled in said cap and said second borerespectively, a detonator in said rotor and disposed normally out ofalignment with said first bore; an unbalanced, arcuate mass integralwith the inner end of said rotor, said mass defining an arcuate cut-outand having a hole therein, said cut-out forming at least one shoulder;means for preventing rotating of said rotor comprising, an angular armpivoted at one of its ends to the underside of said cap and having adownwardly depending tang integral with the inner side of its free end,a disc having a notch in its circumferential edge, said disc beingsecured on the 'upper'side of said rotor, said tang being in releasableengagement with the notch in said disc; means normally urging said rotorin a counter clockwise direction comprising a'torsion spring having oneofits ends fixed to the upper end of said shaft; its other end beingsecured to said "cap; and detent means for locking said rotor when in anarmed position comprising, a spring biased plunger slidably mounted insaid third bore in said body and normally biased into engagement withsaid shoulder on said unbalanced mass, said plunger function ing uponprojectile spin to move into said third bore and toutof engagementwith'said shoulder to release said unbalanced mass, whereupon during setback force, said arm will be caused to rotate rearwardly to move saidtang on said arm out of the notch in said disc to permit said rotor,disc and unbalanced mass to rotate in a clockwise direction due tocontinuing set back force until said set back force ceases, whereuponsaid torsion springwill rotate said rotor in a counter-clockwisedirection until said plunger snaps into said hole in said unbalancedmass to lock said rotor in an armed position, whereby said detonation isin axial alignment in said first bore in said body.

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